1. Technical Field
The present invention relates to a receiving apparatus, an electromagnetic wave timepiece, a receiving module, and a receiving method, which receive a communication signal including time information.
2. Related Art
In an electromagnetic wave timepiece which receives time signal transmitted by means of an electromagnetic wave, and displays accurate time information, a method has been known which receives a standard frequency, in a low frequency band, transmitted from a ground base station, or a time signal, in an ultrahigh frequency band, transmitted from a GPS (Global Positioning System) satellite. Furthermore, recently, as described in JP-A-2000-321383, a timepiece has been proposed which acquires an accurate time by receiving a time signal, included in an electromagnetic wave in an ultrahigh frequency band, which is CDMA (Code Division Multiple Access) modulated and transmitted for the purpose of mobile communication. It has been known that this kind of electromagnetic wave in the ultrahigh frequency band, as it is relayed far and wide by various kinds of repeater, can be received in a good condition even at various movement destinations, such as an inside of a building or underground, in comparison with the standard frequency in the low frequency band, and the electromagnetic wave from the GPS satellite. Also, it has been known that a timepiece which receives a CDMA electromagnetic wave, after demodulating a pilot channel signal and obtaining synchronization with the base station at a reception start time, by demodulating and decoding a sync channel signal, can acquire time information including GPS time, leap second, local offset and daylight-saving time information, and the like.
In the case in which the timepiece receives the CDMA electromagnetic wave, demodulates the pilot channel signal and, after obtaining the synchronization with the base station, decodes the sync channel signal, and acquires the time information, as data strings including the time information continue in regular periods in the sync channel signal, in order to extract the time information from the data strings, it has been necessary to acquire data in a data string from its head. Consequently, the time information has been extracted by detecting the head of the data string from among the decoded data, and acquiring the data from the detected head. However, it has been necessary to continue a receiving operation even for a time period from acquiring initially demodulated sync channel data until acquiring data at the head of a next data string. Consequently, as considerable power is consumed by continuing the receiving operation, it has been difficult to reduce a power consumption of an information processor including this kind of timepiece.